A natural shell-based dental cleaning abrasive particle and a method of making the same

Abstract

The application discloses a natural shell-based tooth cleaning abrasive particle and a preparation method thereof, relates to the technical field of oral care, and discloses the abrasive particle in a core-shell structure, which comprises a core composed of red date core powder and a chitosan layer coated on the surface of the core. The natural shell-based tooth cleaning abrasive particle and the preparation method thereof are characterized in that the core of the abrasive particle is composed of natural red date core powder, the Mohs hardness of the abrasive particle is 2.5-3.5, and the spherical or ellipsoidal smooth surface formed by the chitosan layer realizes the perfect balance between high-efficiency cleaning and low tooth enamel damage. The abrasive particle has the characteristics of being renewable and biocompatible, has no stimulation to human oral mucosa, has no carcinogenic risk in long-term use, has moderate Mohs hardness, has the characteristics of high-efficiency cleaning and low tooth enamel damage, has excellent fluorine compatibility and paste stability after denaturation, can replace or partially replace traditional inorganic abrasives, realizes high-value utilization of waste, and meets the green circular economy concept.

Description

Technical Field

[0001] This invention relates to oral care technology, specifically to a natural shell-based tooth cleaning abrasive particle and its preparation method. Background Technology

[0002] Jujube is one of my country's important economic forest fruits, with abundant resources and a huge annual output. Besides being eaten fresh, jujubes are extensively processed into dried dates, date cakes, date juice, candied dates, and other products. During the processing of jujubes, approximately 20% to 30% of the fruit's weight is generated as pits. These pits mainly consist of a hard, lignified outer shell and an inner kernel. Currently, apart from a small amount used to extract active ingredients and prepare activated carbon, the vast majority of jujube pits are discarded or incinerated as solid waste, resulting in a huge waste of biological resources and putting pressure on the ecological environment.

[0003] On the other hand, abrasives are a core component of toothpaste formulations. Currently, the mainstream abrasives in commercially available toothpastes are mineral-based, such as calcium carbonate (calcite powder), silica (hydrated silica), dicalcium phosphate, and aluminum hydroxide.

[0004] Although calcium carbonate is inexpensive, it is relatively hard (Mohs hardness 3-4), and its crystals are mostly acute-angled rhomboid. Long-term use can easily cause scratches on the enamel surface (one of the potential causes of "brushing wedge defects" often mentioned in clinical practice). In addition, it is chemically active and easily reacts with fluoride ions in toothpaste to form calcium fluoride precipitate, causing the effective anti-caries ingredients in toothpaste to become ineffective.

[0005] Although silica (hydrated silica) has the advantages of controllable abrasion value, good compatibility with fluoride, and delicate taste, its production process is complex and energy-intensive, resulting in its market price being several to dozens of times that of calcium carbonate, which greatly increases the production cost of toothpaste companies.

[0006] It is worth noting that the safety of some traditional toothpaste ingredients has received widespread attention in recent years. While calcium carbonate is widely used as an abrasive, its high hardness and sharp crystal structure pose potential mechanical damage to tooth enamel. Triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether), a broad-spectrum antibacterial agent, has been the subject of numerous studies suggesting it may interfere with the human endocrine system, posing potential health risks with long-term use. Titanium dioxide (titanium white), used as a toothpaste whitening agent, has also been the subject of controversy regarding the cumulative effect of its nanoparticles in the body and their potential carcinogenicity. Therefore, developing a toothpaste abrasive that is naturally derived, safe in composition, and free of toxic side effects is of significant practical importance. Finding a novel abrasive that is widely available, inexpensive, renewable, biocompatible, and functional has always been a research hotspot in the oral care industry. This invention, based on this background, innovatively proposes a natural shell-based tooth-cleaning abrasive particle, achieving high-value utilization of agricultural byproducts and a green upgrade of oral care products. Summary of the Invention

[0007] The purpose of this invention is to provide a natural shell-based tooth cleaning abrasive particle and its preparation method, in order to solve the problems of inorganic abrasives easily damaging tooth enamel and having poor fluoride compatibility in the prior art, as well as the insufficient stability of paste when natural plant-derived materials are directly applied.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a natural shell-based abrasive particle body for teeth cleaning, wherein the abrasive particle body has a core-shell structure, comprising: a core composed of jujube pit powder, and a chitosan layer covering the surface of the core; the average particle size D50 of the abrasive particles is 3-15 μm, the thickness of the chitosan layer is 0.1-2 μm, and the Mohs hardness is 2.5-3.5.

[0009] Furthermore, the jujube kernel powder is derived from at least one of gray jujube, Jun jujube, Hami jujube or golden thread jujube, the lignin content of the jujube kernel powder is not less than 25%, the chitosan molecular weight of the chitosan layer is 3000-200000 Da, and the degree of deacetylation is not less than 80%.

[0010] Furthermore, the surface of the abrasive particles is spherical or ellipsoidal, with a surface roughness Ra≤0.5μm, a smooth and rounded surface, no sharp edges, and a moisture content of less than 5%.

[0011] Furthermore, the chitosan layer coats the core surface to form a hydrophobic layer, the water contact angle of the abrasive particle body is ≥90° and the water content is less than 5%. This hydrophobic layer can block the excessive adsorption of water and fluoride ions, so that the toothpaste containing the abrasive particles does not show water separation after being stored at 45°C for 3 months, and the free fluoride retention rate is not less than 90%.

[0012] Furthermore, the abrasive particles also include other abrasive particles in combination, wherein the other abrasive particles are selected from at least one of silica particles and calcium carbonate particles, and the mass ratio of the other abrasive particles to the main body of the natural shell-based dental cleaning abrasive particles is 1:10 to 10:1.

[0013] A method for preparing natural shell-based dental cleaning abrasive particles includes the following steps:

[0014] Step 1, Pre-treatment and crushing: Collect natural plant fruit shells, remove residual pulp, kernels and other impurities, wash and dry until the moisture content is less than 6%, then coarsely crush to obtain coarse fruit shell particles;

[0015] Step 2, Ultrafine Grinding and Grading: The coarse fruit shell particles obtained in Step 1 are ultrafinely ground by a vibratory mill or bead mill, and then classified by air classifier or sieve to collect fruit shell ultrafine powder with an average particle size D50 of 3 to 15 μm.

[0016] Step 3: Chitosan denaturation treatment: The ultrafine shell powder obtained in Step 2 is immersed in a chitosan solution, and the solid-liquid mass ratio is controlled at 1:2 to 1:5. The mixture is stirred and reacted for 30 to 90 minutes. After filtration, it is vacuum dried at 50 to 70°C until the water content is less than 5%, thus obtaining the abrasive particle body.

[0017] Further, the chitosan solution is prepared by dissolving chitosan in an aqueous acetic acid solution with a volume fraction of 0.5% to 2.0% to prepare a chitosan solution with a mass fraction of 1% to 10%, and adjusting the pH to 4.5 to 5.5.

[0018] Furthermore, the drying method in step one is hot air drying or microwave drying; the pulverizing pressure of the ultrafine pulverizer in step two is 0.5-1.0 MPa, and the speed of the classifying wheel is 3000-5000 rpm.

[0019] Compared with the prior art, the natural shell-based tooth cleaning abrasive particles and their preparation method provided by the present invention have the following beneficial effects:

[0020] Firstly, regarding the friction cleaning performance, the core of the abrasive particles in this invention is composed of natural jujube pit powder, with a Mohs hardness of 2.5–3.5. Combined with the spherical or ellipsoidal smooth surface formed by the chitosan layer, a perfect balance between highly efficient cleaning and low enamel damage is achieved. According to ISO 11609 standard testing, toothpaste containing these abrasive particles has a PCR value of 85–92, comparable to or slightly higher than calcium carbonate abrasive (PCR=88), while its RDA value is only 78–85, far lower than the 125 of calcium carbonate abrasive, achieving a low abrasion level close to that of expensive silica abrasive (RDA=70), truly realizing a "highly efficient and low-damage" cleaning effect. Secondly, regarding product stability, the chitosan layer, by forming a hydrophobic modified layer with a thickness of 0.1–2 μm on the particle surface, effectively blocks the excessive adsorption of moisture and fluoride ions by plant fibers. Experiments have shown that toothpaste containing this abrasive particles, after 3 months of accelerated storage at 45°C, retains at least 90% of its free fluoride content. The paste exhibits no water separation, thickening, or mold growth, significantly outperforming unmodified jujube pit powder (82% fluoride retention, with thickening and water separation), fully meeting the shelf-life requirements for toothpaste products. This synergistic improvement in cleaning and stability is the core technological advantage of this invention achieved through its "core-shell" structural design, overcoming the common technical challenges of paste deterioration and poor fluoride compatibility when natural plant-derived materials are directly applied to toothpaste systems.

[0021] This invention is the first to transform a large amount of waste date pits (approximately 20%–30% of the fruit weight) generated during date processing into a high-value-added oral care raw material. Traditionally, these date pits are discarded or incinerated as solid waste, causing serious waste of biological resources and environmental pollution. This invention, through a three-step process of "pretreatment crushing—ultra-micro pulverization and grading—chitosan denaturation treatment," transforms this zero-cost or even negative-cost agricultural byproduct into a high-performance dental cleaning abrasive, achieving "turning waste into treasure." The raw material cost is only 1 / 5 to 1 / 10 of that of silica abrasives, bringing significant economic benefits to toothpaste companies and aligning with the national green circular economy development strategy. Furthermore, the abrasive particles of this invention are of pure natural organic origin, with a core of date pit powder and a shell of chitosan, both exhibiting good biodegradability and biocompatibility. The product does not contain calcium carbonate, triclosan, titanium dioxide, or other ingredients with controversial safety profiles. Testing has shown no irritation to the oral mucosa, cytotoxicity level 0, and no carcinogenic risk with long-term use. Furthermore, the chitosan layer itself possesses broad-spectrum antibacterial activity, exhibiting an inhibition zone diameter ≥12mm against Streptococcus mutans, which can assist in inhibiting cariogenic bacteria. This invention successfully develops waste jujube pits into a toothpaste abrasive that combines cleaning, safety, antibacterial, and natural health benefits, providing a novel green solution for the oral care industry and demonstrating promising industrial application prospects and promotional value. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 This is a three-dimensional view of the external structure of the abrasive particles of the present invention;

[0024] Figure 2 This is a three-dimensional view of the internal structure of the abrasive particles of the present invention;

[0025] Figure 3 This is a flowchart illustrating a method for preparing natural shell-based tooth cleaning abrasive particles according to the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Abrasive particle body; 101. Core; 102. Chitosan layer. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] Please see Figure 1 and Figure 2 As shown, the present invention provides a natural shell-based tooth cleaning abrasive particle. The abrasive particle body 1 has a core-shell structure, including: a core 101 composed of jujube pit powder, and a chitosan layer 102 covering the surface of the core 101; the average particle size D50 of the abrasive particle body 1 is 3 to 15 μm, and the Mohs hardness is 2.5 to 3.5.

[0031] Jujube kernel powder is derived from at least one of gray jujube, Jun jujube, Hami jujube or golden thread jujube. The lignin content of the jujube kernel powder is not less than 25%, and the chitosan molecular weight of chitosan layer 102 is 3000-200000 Da, with a degree of deacetylation of not less than 80%.

[0032] The thickness of the chitosan layer 102 is 0.1–2 μm.

[0033] The surface of the abrasive particle body 1 is spherical or ellipsoidal, with a surface roughness Ra≤0.5μm, smooth and rounded surface, no sharp edges, and moisture content less than 5%.

[0034] The chitosan layer 102 wraps around the surface of the core 101 to form a hydrophobic layer. The water contact angle of the abrasive particle body 1 is ≥90° and the water content is less than 5% (the cross-section observed by scanning electron microscopy shows that the chitosan layer has no visible pores). This hydrophobic layer can prevent excessive adsorption of water and fluoride ions, so that the toothpaste containing the abrasive particles does not show water separation after being stored at 45°C for 3 months, and the free fluoride retention rate is not less than 90%.

[0035] The abrasive particle body 1 also includes other abrasive particles, which are selected from at least one of silica particles and calcium carbonate particles. The mass ratio of the other abrasive particles to the natural shell-based dental cleaning abrasive particle body 1 is 1:10 to 10:1.

[0036] Everyday cleaning-grade natural shell-based abrasive particles were produced by removing impurities from jujube pits, drying, and coarsely crushing them, followed by ultrafine grinding and grading using a vibratory mill to collect ultrafine jujube pit powder with an average particle size D50 = 8.5 μm. A 5% chitosan solution (dissolved in 1% acetic acid, pH adjusted to 5.0) with a molecular weight of 30000 Da and a degree of deacetylation of 90% was prepared and used to impregnate the ultrafine jujube pit powder at a solid-liquid ratio of 1:3. The mixture was stirred and reacted for 60 minutes, filtered, and then vacuum-dried at 60°C until the water content was <5%. The resulting abrasive particles were spherical with a smooth surface and a Mohs hardness of approximately 3.0 (calculated using a micro Vickers hardness conversion method). When added to toothpaste at a mass fraction of 20% (formula shown in Application Example 1 below), the RDA value was 78 and the PCR value was 85 according to ISO 11609 standards. After accelerated storage at 45°C for 3 months, the fluoride retention rate was 90%, and the toothpaste showed no water separation or thickening.

[0037] Application Example 1: Daily cleaning toothpaste containing natural shell-based abrasive particles 1

[0038] Formula (mass fraction):

[0039] Example 1: Abrasive particles: 20%;

[0040] Sorbitol (70%): 45%;

[0041] Sodium carboxymethyl cellulose: 1.0%;

[0042] Xanthan gum: 0.3%;

[0043] Sodium saccharin: 0.2%;

[0044] Sodium monofluorophosphate: 0.8%;

[0045] Sodium dodecyl sulfate: 2.0%;

[0046] Peppermint flavoring: 1.0%;

[0047] Sodium benzoate: 0.2%;

[0048] Deionized water: Add to 100%.

[0049] Preparation process: Sodium carboxymethyl cellulose and xanthan gum are dispersed in sorbitol to form a gel solution; sodium saccharin, sodium benzoate, and sodium monofluorophosphate are dissolved in deionized water; the aqueous phase and gel solution are mixed evenly in a paste-making pot, and abrasive particles (body 1) are added. The mixture is stirred at high speed under a vacuum of 0.096 MPa for 30 minutes; finally, sodium dodecyl sulfate and fragrance are added, and the mixture is further degassed under vacuum for 15 minutes before filling. The resulting toothpaste has a fine texture, rich foam, and a refreshing taste.

[0050] Performance testing

[0051] Comparative Example 1

[0052] A commercially available toothpaste containing calcium carbonate abrasive was selected as comparative example 1.

[0053] Comparative Example 2

[0054] A commercially available toothpaste containing silica (hydrated silica) abrasive was selected as comparative example 2.

[0055] Comparative Example 3

[0056] The formula and process of Application Example 1 were followed, but the modified jujube kernel powder was replaced with unmodified jujube kernel powder, as Comparative Example 3.

[0057] Friction value and cleaning efficiency test: Refer to ISO 11609 standard and use in vitro methods to test PCR (pellicle cleaning ratio) and RDA (radioactive dentin abrasion).

[0058] Toothpaste stability test: Place the toothpaste sample in a 45℃ constant temperature chamber and observe the appearance, water separation and viscosity changes of the paste after 3 months.

[0059] Fluoride stability test: The free fluoride content of toothpaste was determined according to GB / T 8372-2017 standard, both in the initial and accelerated aging stages.

[0060] Antibacterial activity test: The antibacterial effect of toothpaste slurry on Streptococcus mutans was tested using the agar diffusion method.

[0061] The test results are summarized in the table below:

[0062] Group Main abrasive PCR value RDA value Fluorine retention rate after 3 months (%) Ointment stability (45℃, 3 months) Application Example 1 Transgenic jujube pit powder 85 78 90 The paste is fine and has no water separation. Comparative Example 1 Calcium carbonate 88 125 65 Slight water separation Comparative Example 2 silicon dioxide 82 70 92 The paste is fine and has no water separation. Comparative Example 3 Undenatured jujube kernel powder 84 80 82 The paste thickened, and water separated on the surface.

[0063] The test results above show that:

[0064] Excellent friction performance: The cleaning efficiency of Application Example 1 is comparable to that of calcium carbonate, but the wear value is much lower than that of calcium carbonate, approaching the level of expensive silica, thus achieving "high efficiency and low loss".

[0065] Necessity of denaturation: The denatured jujube kernel powder (Application Example 1) is significantly better than the undenatured jujube kernel powder (Comparative Example 3) in terms of fluoride compatibility and paste stability, proving that surface denaturation is a key technical means to solve the problem of applying plant-derived materials to toothpaste systems.

[0066] In summary, the natural shell-based tooth-cleaning abrasive particles 1 prepared in Example 1 of this invention can replace traditional inorganic abrasives, significantly reducing enamel wear (RDA=78) while ensuring high-efficiency cleaning (PCR=85), which is superior to calcium carbonate (RDA=125). Fluoride compatibility and paste stability reach levels comparable to silica, and it overcomes the paste deterioration problem of undenatured jujube pit powder, fully meeting the shelf-life requirements of toothpaste products. It also has no oral mucosal irritation and additional antibacterial function. Furthermore, the prepared abrasive particles 1 are spherical or ellipsoidal in shape, with a smooth and rounded surface after being coated with chitosan, without obvious sharp edges or corners. Compared with traditional calcium carbonate abrasives (mostly irregular blocks or rhomboid shapes), this spherical structure can effectively reduce mechanical stimulation of the gingival tissue during brushing, reducing the risk of gingival abrasion and scratches.

[0067] At the same time, it is made from pure natural organic sources and does not contain ingredients with controversial safety such as calcium carbonate, triclosan, and titanium dioxide. It is non-irritating to the oral mucosa, has no carcinogenic risk with long-term use, has good biocompatibility, and realizes the high-value utilization of agricultural by-products. It has good industrial application prospects and has successfully developed waste jujube pits into a toothpaste abrasive with cleaning, safety and natural health care functions. It has good industrial application prospects and economic benefits.

[0068] Example 2

[0069] Based on Example 1, please refer to Figure 1 and Figure 2 As shown, highly efficient stain-removing natural shell-based abrasive particles were produced by pulverizing and classifying jujube pits using a bead mill after impurity removal, drying, and coarse crushing, resulting in ultrafine powder with an average particle size (D50) of 5.0 μm. An 8% chitosan solution (dissolved in 1.5% acetic acid, pH adjusted to 4.8) with a molecular weight of 10000 Da and a degree of deacetylation of 95% was prepared and used to impregnate the jujube pit ultrafine powder at a solid-liquid ratio of 1:2. The solution was stirred and reacted for 45 minutes, then filtered and vacuum-dried at 55°C until the water content was <5%. The resulting abrasive particles had a finer main particle size and a denser surface coating. When added to toothpaste at a mass fraction of 40%, the RDA value was 85, and the PCR value was as high as 92. It showed significant effectiveness in removing extrinsic stains such as tea stains and tobacco stains, and maintained 88% fluoride retention after 3 months of storage at 45°C, demonstrating stability in the toothpaste.

[0070] Application Example 2: Tooth polishing paste containing natural shell-based abrasive particles (for professional oral care)

[0071] Formula (mass fraction):

[0072] Product Example 2: Abrasive particles: 35%;

[0073] Glycerin: 30%;

[0074] Propylene glycol: 10%;

[0075] Hydroxyethyl cellulose: 1.5%;

[0076] Polosham 407: 2.0%;

[0077] Xylitol: 1.0%;

[0078] Zinc citrate: 0.5%;

[0079] Deionized water: Add to 100%.

[0080] Preparation process: Hydroxyethyl cellulose is dispersed in glycerol and propylene glycol; poloxamer 407, xylitol, and zinc citrate are dissolved in water; the two phases are mixed, and the abrasive particles are added. The mixture is then uniformly dispersed under high shear, degassed under vacuum, and filled into a dental syringe. This polishing paste is used in dental clinics with a rubber cup on a low-speed bending head. It effectively removes tooth surface stains and early plaque without damaging tooth enamel or gums.

[0081] Example 3

[0082] Please see Figure 3 As shown, a method for preparing natural shell-based tooth cleaning abrasive particles includes the following steps:

[0083] Step 1, Pre-treatment and crushing: Collect natural plant fruit shells, remove residual pulp, kernels and other impurities, wash and dry until the moisture content is less than 6%, then coarsely crush to obtain coarse fruit shell particles;

[0084] Step 2, Ultrafine Grinding and Grading: The coarse fruit shell particles obtained in Step 1 are ultrafinely ground by a vibratory mill or bead mill, and then classified by air classifier or sieve to collect fruit shell ultrafine powder with an average particle size D50 of 3 to 15 μm.

[0085] Step 3, Chitosan Modification Treatment: The ultrafine shell powder obtained in Step 2 is immersed in a chitosan solution, and the solid-liquid mass ratio is controlled at 1:2 to 1:5. The mixture is stirred and reacted for 30 to 90 minutes. After filtration, it is vacuum dried at 50 to 70°C until the water content is less than 5%, thus obtaining the abrasive particle body 1.

[0086] The chitosan solution is prepared by dissolving chitosan in an aqueous acetic acid solution with a volume fraction of 0.5% to 2.0% to prepare a chitosan solution with a mass fraction of 1% to 10%, and adjusting the pH to 4.5 to 5.5.

[0087] In step one, the drying method is hot air drying or microwave drying; in step two, the pulverizing pressure for ultrafine grinding is 0.5-1.0 MPa, and the classifying wheel speed is 3000-5000 rpm.

[0088] Standard preparation method:

[0089] 1. Collect the jujube pits, remove residual pulp and kernels by screening, with a total impurity content of <1%, dry with hot air at 60℃ to a moisture content of 5%, and crush into 2-5mm particles using a hammer mill.

[0090] 2. The crushed particles are fed into a vibratory mill with a crushing pressure of 0.8 MPa and a classifying wheel speed of 4000 rpm. The ultrafine powder is collected and measured by a laser particle size analyzer, with D50=8.5μm and D90<20μm.

[0091] 3. Take 10 kg of the above ultrafine powder, place it in a reaction vessel, add 30 kg of 5% chitosan solution (molecular weight 30000 Da, degree of deacetylation 90%, soluble in 1% acetic acid, pH 5.0), solid-liquid ratio 1:3, stir and react for 60 minutes, filter, and dry in a vacuum drying oven at 60℃ until the water content is 4.5%, and the product is obtained.

[0092] Example 4

[0093] Please see Figure 3 As shown, the preparation method for large particle size and low degree of denaturation is as follows:

[0094] 1. Collect the pits of the golden thread jujubes, microwave them until the moisture content is 4%, and crush them into 3-6mm particles;

[0095] 2. A vibratory mill was used, with a crushing pressure of 0.6 MPa and a classifying wheel speed of 3000 rpm, to collect ultrafine powder with a D50 of 12 μm;

[0096] 3. Take 10 kg of ultrafine powder and add 40 kg of 3% chitosan solution (molecular weight 50000 Da, degree of deacetylation 85%, soluble in 0.8% acetic acid, pH 5.2), with a solid-liquid ratio of 1:4. Stir and react for 90 minutes, filter, and vacuum dry at 50℃ until the water content is 3.8%. The resulting particles are suitable for low-friction sensitive teeth care products.

[0097] Example 5

[0098] Please see Figure 3 As shown, the preparation method for small particle size and high degree of denaturation is as follows:

[0099] 1. Collect the pits of Hami jujubes, dry them with hot air until the moisture content is 3.5%, and crush them into 1-3mm particles;

[0100] 2. The powder was wet-milled using a bead mill (zirconia beads, 0.5 mm in diameter) for 120 minutes, sieved, and then centrifuged and dried to obtain an ultrafine powder with a D50 of 3.2 μm.

[0101] 3. Take 10 kg of ultrafine powder and add 20 kg of 10% chitosan solution (molecular weight 8000 Da, degree of deacetylation 92%, soluble in 2% acetic acid, pH 4.5), with a solid-liquid ratio of 1:2. Stir and react for 30 minutes, filter, and vacuum dry at 70℃ until the water content is <5%. The resulting particles have extremely high specific surface area and strong antibacterial properties, making them suitable for professional stain-removing toothpaste.

[0102] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A natural shell-based abrasive particle for tooth cleaning, characterized in that, The abrasive particle body (1) has a core-shell structure, including: a core (101) made of jujube pit powder, and a chitosan layer (102) covering the surface of the core (101); the average particle size D50 of the abrasive particle body (1) is 3 to 15 μm, the thickness of the chitosan layer (102) is 0.1 to 2 μm, and the Mohs hardness is 2.5 to 3.

5.

2. The natural shell-based tooth-cleaning abrasive particles according to claim 1, characterized in that, The jujube kernel powder is derived from at least one of gray jujube, Jun jujube, Hami jujube or golden thread jujube. The lignin content of the jujube kernel powder is not less than 25%, and the chitosan layer (102) has a chitosan molecular weight of 3000 to 200000 Da and a degree of deacetylation of not less than 80%.

3. The natural shell-based tooth-cleaning abrasive particles according to claim 1, characterized in that, The surface of the abrasive particle body (1) is spherical or ellipsoidal, with a surface roughness Ra≤0.5μm, no sharp edges, and a moisture content of less than 5%.

4. The natural shell-based tooth-cleaning abrasive particles according to claim 1, characterized in that, The chitosan layer (102) wraps around the surface of the core (101) to form a hydrophobic layer, and the water contact angle of the abrasive particle body (1) is ≥90° and the water content is less than 5%.

5. The natural shell-based tooth-cleaning abrasive particles according to claim 1, characterized in that, The abrasive particle body (1) also includes other abrasive particles, which are selected from at least one of silica particles and calcium carbonate particles, and the mass ratio of the other abrasive particles to the natural shell-based tooth cleaning abrasive particle body (1) is 1:10 to 10:

1.

6. A method for preparing natural shell-based dental cleaning abrasive particles according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1, Pre-treatment and crushing: Collect natural plant fruit shells, remove residual pulp, kernels and other impurities, wash and dry until the moisture content is less than 6%, then coarsely crush to obtain coarse fruit shell particles; Step 2, Ultrafine Grinding and Grading: The coarse fruit shell particles obtained in Step 1 are ultrafinely ground by a vibratory mill or bead mill, and then classified by air classifier or sieve to collect fruit shell ultrafine powder with an average particle size D50 of 3 to 15 μm. Step 3, Chitosan denaturation treatment: The ultrafine shell powder obtained in step 2 is immersed in chitosan solution, the solid-liquid mass ratio is controlled at 1:2 to 1:5, the mixture is stirred and reacted for 30 to 90 minutes, filtered and then vacuum dried at 50 to 70°C until the water content is less than 5%, thus obtaining the abrasive particle body (1).

7. The method for preparing natural shell-based tooth cleaning abrasive particles according to claim 7, characterized in that, The chitosan solution is prepared by dissolving chitosan in an aqueous acetic acid solution with a volume fraction of 0.5% to 2.0% to prepare a chitosan solution with a mass fraction of 1% to 10%, and adjusting the pH to 4.5 to 5.

5.

8. The method for preparing natural shell-based tooth cleaning abrasive particles according to claim 7, characterized in that, In step one, the drying method is hot air drying or microwave drying; in step two, the pulverizing pressure for ultrafine grinding is 0.5-1.0 MPa, and the speed of the classifying wheel is 3000-5000 rpm.

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